Multi-ply liner bags



Feb. 25, 1964 J. P. SACHS 3,122,297

MULTI-PLY LINER BAGS Filed Oct. 23, 1961 3 Sheets-Sheet 1 INVENTOR. JOHNP. SACHS ATTORNEY Feb. 25, 1964 INVENTOR JOHN P. SACHS ATTORNEY Feb. 25,1964' J. P. sAcHs 3,122,297

MULTI-PLY LINER BAGS Filed Oct. 25, 1961 3 Sheets-Sheet 3 M INVENTOR.($194K JOHN RSACHS ATTORNEY United rates Patent Oflice 3,l22,2fl?Fatented Feb. 25, 1964 3,122,297 MULTl-PLY LINER BAGS John P. Sachs, LaGrange, ill, assignor to Union (Jarbide Corporation, a corporation ofNew York Filed Get. 23, 1961, Ser. No. 146,744 1t} tilaims. (CL 229-44)This invention relates to a multi-ply thermoplastic film liner bag andthe method of forming the same, and furthermore, this invention relatesto the use of said multi-ply liner bag in a rigid container forshipping, storing and dispensing such diverse items as milk, fruitjuices, syrups and other liquids, as well as ice cream and pasty andpulverulent materials.

In an attempt to overcome the deficiencies of using metal, glass andwax-lined cardboard containers for shipping, storing and dispensingflowable materials, such as milk, plastic film liner bags shaped andsupported in a rigid container commonly made of corrugated paper, arebeing used.

At the dairy, the plastic film liner bag generally having a filling andpouring spout is placed in the corrugated paper container and filledwith milk. The container is then distributed, as a package, torestaurants and institutions for dispensing the milk therefrom. At therestaurant, the pouring spout is withdrawn from the package, and thepackage is set into a conventional refrigerated dispenser unit in aninverted position, and the pouring spout is passed through a (pinchclamp) dispensing valve.

In using such liner bags of plastic film for shipping milk, a highincidence of liner leakage has resulted from efects particularlypinholes in the plastic liner bag, caused by a variety of factors mostof which are related to the severity of the conditions in shipping milkin a plastic liner bag, within a rigid container, over rough countryroads from the dairy to the user. Pinholes below the liquid level withinthe plastic liner bag cannot be tolerated because of leakage duringshipment. Pinholes at or above the liquid level line within the plasticliner bag are objectionable because when the package is inverted fordispensing, leakage will occur.

The presence of pinholes in the plastic film of the liner bag has beenfound to primarily result from environmental stress corrosion and flexfatigue of the plastic film, especially where folds in the film existed.Such adverse efiects are related to normal shipping motion which sloshesor moves the milk in and about the bag, thereby producing the physicalellects of Wave vibration and hydraulic hammer that result in theenvironmental stress corrosion of flex fatigue. The physical effects ofwave vibrations and hydraulic hammer have been found to be particularlyconcentrated in folds in the plastic film of the liner bag, flexing andunflexing said film folds; and this is Where the greatest damage due toenvironmenta stress corrosion and flex fatigue has occurred.

Also, the lactic acid and butter fat content or" the liquid milk tend toreact chemically with the plastic film of the liner bag and causeenvironmental stress corrosion and flex fatigue in the liner walls,particularly at or above the normal liquid level within the liner bag.In addition, punctures or abrasion in the liner bag from handling andcontact with the rigid container, have contributed to the high incidenceof pinholes in the liner bags of plastic film.

Furthermore, any slight leakage of the liquid-filled plastic liner bagis accentuated by the absorptive attraction of the supporting corrugatedpaper walls of the rigid container, and by the hydraulic head of theliquid contents on the pinhole.

Additionally, in using such liner bags for shipping milk or otherperishable food products, if the bags are not formed with an essentiallysterile interior and maintained in such condition, undesirable flavor,odor and bacterial growth tend to be imparted to said products.

Among the objects of the present invention are to pro vide a novelmulti-ply liner bag of flexible thermoplastic lm for flowable materialsand especially for milk; to provide such a multi-ply flexiblethermoplastic liner bag which is essentially sterile and to a method forforming such a bag; to provide such a multi-ply flexible thermoplasticliner bag which is leakproof; to provide such a multi-ply flexiblethermoplastic liner bag which will resist stress corrosion, flexfatigue, puncture and abrasion from shipping movement, prolonged storagein the inverted position, handling and contact with a rigid containe; toprovide such a bag which is leakproof and will collapse to void all itscontents; to provide such a bag which can be made of a suflicientlyinexpensive material that it can be disposed of after one use, and toprovide such a bag which can be easily and economically made.

The objects of this invention are accomplished in general, by providinga rigid container with a multi-ply leakproof, flexible, collapsibleliner bag having an inner ply of flattened seamless flexiblethermoplastic tubular film, preferably interiorly essentially sterile,an outer film ply of flexible thermoplastic sheeting circumscribed aboutthe inner film ply with the longitudinal free edges of the sheeting heatsealed together, thereby forming a tubing concentric with the inner ply,and with the coextensive ends of the inner and outer film plies heatsealed together, said multi-ply bag having an opening therein forcommunicating with the interior of said seamless tubular inner film ply.

In the preferred embodiment of this invention, a rigid container isprovided with a multi-ply leakproof, flexible, collapsible liner baghaving an inner film ply of flattened seamless flexible thermoplastictubular film interiorly essentially sterile and a concentric,coextensive outer film ply of centerfolded sheeting circumscribed aboutsaid inner ply. The centerfold of the sheeting which forms the outer plyis juxtaposed along one longitudinal edge of the flattened seamlesstubular film and the free edges of the sheeting opposite said centerfoldare heat sealed together in juxtaposition with the other longitudinaledge of the flattened seamless tubular film. The coextensive ends of theinner and outer plies of flattened seamless tubular film andcenterfolded heat sealed sheeting are sealed together by transverse heatseals, and an opening in said multi-ply liner bag communicates with theinterior of the inner film ply for the passage of flowable material.Preferably one of the transverse heat seals terminates inwardly from onecorner of the film plies, thereby providing an opening or gap for afilling and pouring spout.

The length of the multi-ply thermoplastic liner bag is such as topreferably provide a free board portion to insure filling the flowablematerial, such as milk, to a precise predetermined volume. Accordingly,after filling the multi-ply liner bag with flowable material, the filmwalls comprising the free-board portion can be loosely infolded aboutthe normal milk or other product level.

With respect to a method of forming an interiorly essentially sterilemulti-ply thermoplastic liner bag of the present invention, the interiorof flexible thermoplastic film melt-extruded as seamless tubing issterile. Accordingly, it is preferred to form the liner bags by formingthe inner film ply from a continuous length of such melt-extrudedflattened seamless flexible thermoplastic tubular film. The outerconcentric film ply of the liner bag is formed with sheeting bycenter-folding and circumscribing sheeting about said continuous lengthof flattened seamless tubular film with said center-fold of the sheetingjuxta- LE posed along one longitudinal edge of said flattened seamlesstubular film, heat sealing the free edges of the sheeting opposite saidcenter fold together in juxtaposition with the other longitudinal edgeof said flattened seamless tubular film, transversely heat sealing theconcentric inner and outer film plies of seamless tubular film andcenterfolded heat-sealed tubular sheeting together across the widthsthereof, transversely heat sealing said concentric inner and outer pliestogether spaced from the other transverse heat seal in such manner so asto preferably leave an opening or gap in one corner of said inner andouter film plies, and transversely severing said concentric inner andouter plies of heat sealed seamless tubular film and sheeting into unitmulti-ply bags. A dispensing tube open to the interior or" the inner plyof flattened seamless tubular film and inserted into said opening orgap, is aifixed to said liner bag in such manner that the essentiallysterile condition or" the interior of the multi-ply liner bag ismaintained.

In an alternate embodiment of this invention the multiply leakproof,flexible, collapsible liner bag comprises a concentric outer ply formedof two edge-sealed sheets of flexible thermoplastic film superimposedabout and coextensive with the inner ply of the flattened seamlessinteriorly essentially sterile flexible thermoplastic tubular film. Thelongitudinal free edges of the outer ply sheets are coterminous, and areheat sealed together in juxtaposition with the adjacent flattened edgesof the inner seamless tubular film ply; and the coextensive ends of theinner and outer plies of flattened seamless tubular film andlongitudinally heat sealed sheets are transversely heat sealed togetheras in the preferred embodiment.

in forming the interiorly essentially sterile multi-ply bag of thealternate embodiment the method set forth for the preferred embodimentcan be used, except that the outer concentric film ply is formed bysuperimposing the two sheets about the continuous length of flattenedseamless tubular film and heat sealing the longitudinal free edges ofthe two sheets in juxtaposition with the adjacent edges of the flattenedseamless tubular film.

The nature of the invention and the manner in which it can be practicedwill become clear from the detailed description when taken inconjunction with the accompanying drawings forming this specificationand wherein:

FIG. 1 is a side elevation of the preferred embodiment of the multi-plythermoplastic liner bag of the present invention;

FlG. 2 is an enlarged cross-sectional view of the multiply thermoplasticliner bag of FIG. 1 taken along the lines 22 thereof;

PEG. 3 is an enlarged longitudinal sectional view of the multi-plythermoplastic liner bag of PEG. 1 taken along the lines 3-3 thereof;

FIG. 4 is a pictorial view of a rigid container broken away to show themnlti-ply thermoplastic liner bag of the present invention filled with aflowable material;

FIG. 5 is a side elevation of the alternate embodiment of the multi-plythermoplastic liner bag of the present invention;

FIG. 6 is an enlarged cross-sectional view of the multiply liner bag ofFIG. 5 taken along the lines 6-6 thereof; and

PEG. 7 is an enlarged longitudinal sectional view of the multi-ply linerbag of FIG. 5 taken along the lines 77 thereof.

Referring to the details of the FIGS. 1-3 there is shown a two-ply,leakproof, flexible collapsible thermoplastic liner bag 10 for a rigidcontainer 12, such as shown in FIG. 4. The inner film ply 14 of the bag10 is made of flattened flexible seamless thermoplastic tubular filminteriorly essentially sterile. The outer film ply 16 of the bag it? iscoextensive with the inner ply 14 and is made of center-folded flexiblethermoplastic sheeting circumscribed about said inner ply 1 For a fivegallon capacity th dimensions of the flattened inner seamless tubularfilm 4 are typically 0.0015 inch thick, 2 inches in flat width and 23%inches long; and the dimensions of the outer centerfolded sheeting plyare 0.0015 inch thick, 42 inches in width in its unfolded condition, and23% inches long.

The center-fold 318 of the sheeting forming the circumscribing outer ply16 is juxtaposed along one longitudinal edge of the flattened innerseamless tubular film ply 14 and the free edges 2%? of the sheetingopposite its centerfold 18 are sealed together by a longitud nalcontrolled pressure heat seal 21 in juxtaposition with the otherlongitudinal edge of the flattened inner seamless tubular film ply 14.

The bottom end 22 of the coextensive inner and outer film plies 14, 16is sealed together with a transverse controlled pressure heat seal 24extending across the width of the multi-ply liner bag 10. The top end 26of the coextensive inner and outer film plies 14, 16 is sealed togetherwith a transerse controlled pressure heat seal 28 leaving a inch gapbetween one corner 3% or" the top end film plies l4, l6 and the terminusof the heat seal 28, to provide a flattened opening or gap 32communicating with interior of the inner film ply Such opening 32 isprovided adjacent the center-fold 18 of the sheeting 16 for theinsertion of a filling and pouring spout E4 in the form of a V inchdiameter by 8 inch long rubber tube closed at its outer end 3:5 by aplug (not shown). The filling and pouring tube or spout 34 is insertedinto the opening 32 in an essentially sterile manner and the bag innerand outer film plies 14, 16 of the corner 3% are gathered about therubber tube 34 into overlapped spiralled folds 38 and fastened to therubber tube 34 by a conventional twist wire fastener lil.

To insure filling the multi-ply liner bag it with flowable material,such as milk, to a prior predetermined volume such as 5 gallons, thelength of the multi-ply thermoplastic liner bag it? is such as topreferably provide a free board portion 41, such as about /2 inch.Accordingly, after filling the multi-ply liner bag it? with flowablematerial, the film walls comprising the free board portion 41 can beloosely infolded at the normal milk level as shown in FIG. 4.

Referring to FTGS. 5-7 wherein like reference numerals are used todesignate like elements shown in FIGS. 1-3, except that a prime is usedafter the numeral, a two-ply, leakproof flexible collapsiblethermoplastic liner bag 10 is shown including an inner ply 14 offlattened, essentia ly interiorly sterile seamless flexible thermoplastic tubular film, and a concentric outer ply 16' of two flexiblethermoplastic sheets 17, 19 superimposed about and coextensive with theinner ply '14-.

The inner flattened seamless tubular film ply 14' is centrallypositioned within the two sheets 17, i=9. The longitudinal free edges20' of the sheets 17, .19 are coter minous and are heat sealed 21'together in juxtaposition: with the adjacent edges of fla te ed seamlesstubular film.

The bottom and top ends 22', 26 of the multi-ply liner bag It) are heatsealed with transverse heat seals 24, 8." in the same manner asdescribed and illustrated for multi ply liner bag 1d of FIGS. 13. Thetop end heat seal 28 terminates inwardly from the corner 30' to providea flat tened opening 32 in the liner bag it? for the filling and pouringspout 34, in the form of a tube, about which the film plies 14, 16' aregathered into the overlapped spiralled folds 38' and fastened thereto bythe conven' tional twist wire fastener 45?.

As in FIGS. 1-3, the length of the multi-ply liner bag 10' of concentrictubular film plies 14, 16' is such so as to provide the free boardportion 4-1 which can be loosely infolded to the normal milk level.

Typically, for a five gallon capacity multi-ply liner bag 1d, the innerply 14 of flattened seamless tubular film is 0.0015 inch thick, 20inches in flat width and 23% inches long, while each sheet of the outerply i6 is 0.0015 inch thick, 21 inches wide, and 23% inches long.

In a multi-ply thermoplastic liner bag of the present invention, anyslight leakage of liquid through pinholes of the inner ply is kept to aminimum because the outer ply of film serves as a barrier to isolate thepinhole from the absorptive effect of a rigid container, and thehydraulic head of the liquid contents serves in a self-sealing capacityto press and block the film adjacent the pinhole against the outer filmply to equalize the hydraulic pressure gradient through the pinhole.

The high incidence of liner leakage resulting from defects andparticularly pinholes is also avoided by preferably providing the rigidcontainer with a multi-ply liner bag comprising an inner ply of flexiblethermoplastic film and preferably polyolefin film resistant toenvironmental stress corrosion and flex fatigue, especially in the filmfolds, and an outer ply of flexible thermoplastic film and preferablypolyolefin film resistant to abrasion and puncture; particularly causedby handling and contact with a rigid container.

Multi-ply liner bags of polyolefin film plies having inner and outerfilm plies with the particular properties herein described, areadmirably suited for containing flowable materials and particularlyperishable materials, such as milk. Among the reasons the multi-plyliner bags of the invention are admirably suited for the describedpurposes is that the physical elfects in normal usage of wave vibrationand hydraulic hammer on the inner film ply do not result n adverse filmdefects due to environmental stress corrosion and flex fatigue. This isparticularly true in any folds in the multi-ply liner bag, such as theinfolded free board portion 41 or 41 of bag or 10, respectively, evenwith the flexing and unfiexing of said folds incurred during normalshipping movement. Secondly, the inner film ply is not adverselyaffected because of contact with the lactic acid and butter fat contentof the liquid milk. Thirdly the outer ply of the multi-ply bag resistspunctures or abrasion, particularly resulting from handling of the bag,and contact of said bag with the rigid container. Fourthly, the interiorof thermoplastic film mel-extruded into seamless tubing, such as by theblown-tube method described in U.S. Patent 2,461,975, is essentiallysterile and does not impart undesirable flavor, odor and bacterialgrowth to the product.

Moreover, multi-ply polyolefin liner bags having the aforedescribedproperties, are admirably suited for containing flowable materials, suchas milk, because they are heat scalable to prevent leakage thereof. Inaddition, a multi-ply liner bag of such polyolefin film plies isflexible and will collapse to void all its contents and is asufiiciently inexpensive material that it can be disposed of after oneuse.

Of particular preference for a liner bag for the shipping and dispensingof milk in a rigid container, is a multiply construction comprising incombination, an inner ply of polyethylene seamless tubular film that hasa high tensile strength and flex modulus and is interiorly essentiallysterile, and an outer ply of a polyethylene film that has a relativelyhigh tear strength and elongation to break and a low coeflicient offriction and is non-conjoint and non-laminated to the inner ply. Amulti-ply liner bag having such an inner ply is resistant toenvironmental stress corrosion and flex fatigue and does not impartundesirable flavor, odor and bacterial growth to the products containedtherein. Additionally, a multi-ply liner bag having such an outer ply isresistant to puncture and abrasion.

To obtain a multi-ply liner bag with the necessary combination ofproperties herein described, it is preferred to have an inner ply madeof a high molecular Weight film-forming polyethylene resin having anintrinsic viscosity of at least about 1.0 and preferably of about 1.0 to2.5 and optimumly about 1.3 to 2.0; a melt index of less than about 2.0and preferably less than about 0.20 and optimurnly about 0.05 to 0.10; adensity of not greater than 0.935 and preferably less than 0.925 andformed into tubular film such as by the blown-tube method described inU.S. Patent 2,461,975. In such a construction, a multi-ply liner bag ispreferred wherein the outer ply is made of film-forming polyethyleneresin having an intrinsic viscosity of at least about 0.6 and optimumlygreater than about 1.0; a melt index of less than about 10.0 andpreferably less than about 2.0; a density of preferably not more than.935; and which when formed into film, is resistant to puncture andabrasion and has a low coefiicient of friction.

Surprisingly, multi-ply liner bags and particularly multi-ply liner bagscomprising, in combination an inner ply made of the polyethylene, hereindescribed and thereafter formed by the blown-tube method and an outerply made of the polyethylene herein described, have been found to avoidthe high incidence of defects which produce the undesired leakage to asignificantly greater extent than single ply film liner bags.

This is clearly shown by a shipping and storage test for leaks thatshows good agreement With actual shipping conditions of milk in trucksoperated over country roads, followed by a storage period. Thissimulated shipping-storage test is conducted by filling the liner in therigid container with 45 F. tap water, closing it off and placing it on aplatform which is vertically oscillated a distance of one inch at 300vibrations per minute in a succession of three minute vibration cyclesand thereafter subjecting it to a 480 minute storage period. Each cyclewas considered to be the equivalent of miles of truck shipping overcountry roads.

The following tables show the results of such leakage for liner bagsmade of multi-ply bags of the present invention as compared to singleply bags employing the same films.

Table 1 sets forth the polyethylene resin properties of the films usedto form the bags. Table II sets forth the percentage of bags survivingsuch a vibration and storage test. Table III sets forth suitable filmproperties for the inner and outer film plies of the multi-ply liner bagof the present invention.

TABLE I Properties of Resins From Which Polyethylene Films are FormedPolyethylene Intrinsic Melt Density Resin Viscosity Index A -l 1.3 0.097.920 B 0. 8 1. 60 919 TABLE H Liquid-Filled Liner Bags SurvivingVibration-Storage Test 1 EXAMPLE OF TWO-FLY BAGS OF THIS INVENTION Typeof Liner Bags Percent of Liner Bags With No Leaks Test Polyethy- FilmPly Thickness 12 Minutes 480 lene Resm (inches) Vibration MinutesStorage A Two ply: 2

.0015 inner ply 1 {B .0o1 outer ply l 100 01 s3 s3 CONTROL BAGS 4 A .003single ply 16 16 5 B .003 single ply 20 20 1 Vibration test abovedescribed.

2 Two-ply bags of construction herein described and shown in Figs. 4-6.2 made from seamless tubing such as described in U.S. Patent ,4 Fburthree minute vibration cycles.

TABLE 111 Physical Properties of Polyethylene Film Formed by the BlownTube Method Film Impact Polyethylene Tbick- Tensile Strength FlexModulus Elongation To Break (1n. Coeft. Of

Resin ness (p.s.i.) (p.s.i.) (Percent) lb./1nil) Friction (inches) M.D.T.D. M.D. T.D. M.D. T.D.

A .0014 2 4,300 2 4, 400 2 27,100 2 32, 000 660 1,160 24. 7 46 B .00152, 620 2, 360 15, 100 17, 900 862 3 l 130 8. 9 .35

1 Blown tube method, such as described in U.S. Patent 2,461,975 whereinthe blow ratio was 12 transverse direction to 4 machine direction.

2 Desirable tensile strength, flex modulus for inner film ply of presentinvention. 3 Desirable elongation to break and coefiicient of frictionfor outer film ply or present invention.

4 M.D. (Machine Direction), T.D. (Transverse Direction).

The test methods determining the values and units for such values setforth herein and particularly in Tables I and III are:

Tensile strength (in pounds per square inch) as measured by testprocedure ASTM D882-56T Flex modulus at 1% elongation (in pounds persquare inch) as measured by test procedure ASTM D1530- 5ST Elongation tobreak (in percent) as measured by test procedure ASTM D882-56T modifiedto be conducted at 135 C.

Impact (inch pounds per mil) at room temperature as measured by a 2.3pound steel ball dropped 2.58 feet, (Modern Packaging, p. 150, June1054).

COClfiClfillt of friction (film-to-filrn) is the numerical result ofdividing the force in grams required to slide 4.5 square inches of filmof the same composition at a rate of 24 inches per minute and under aWeight load of 240 grams in sliding contact, by 240.

Intrinsic viscosity (in deliciters per gram) as measured by testprocedure ASTM D160158T Melt index (flow in grams per minutes) asmeasured by test procedure ASTM D1238-52T Density (in grams per cubiccentimeter) in a gradient column made up of water, methanol, and sodiumacetate at 25 C.

It will be noted from the above Table II that the percent ofliquid-filled liner bags surviving the vibration tests increasedmarkedly as the construction was changed from a single ply bag of 3 milthickness of tests 4 and 5 to an equivalent multi-ply construction oftwo plies each of 1 mil thickness. Furthermore, it is to be noted thatthe multi-ply combination of two similar films, made from the sameresin, was not as eilective in surviving the vibration test as themulti-ply construction using film A as an inner ply and film B as anouter ply.

Table III shows that films, such as polyethylene film type A,characterized by high tensile strength and flex modulus and employed asan inner ply of a multi-ply liner bag, in combination with films such aspolyethylene film type B, characterized by high resistance to percentelongation to break and a 10W coefficient of friction and employed as anouter ply of a multi-ply liner bag, provided a multi-ply liner bagwherein no bags failed due to leakage when subjected to a vibration testsimulating actual shipping conditions.

Table 1 shows the intrinsic viscosity, melt and density characteristicsof the film-forming resins for a preferred embodiment of multi-ply linerbag. An important physical characteristic of film-forming polyolefinresins, such as used in the preferred embodiment, is the intrinsicviscosity. Polyethylene film A is preferably made for a film-formingresin that has an intrinsic viscosity of at least about 1.0,characteristic of a resin that has a high molecular weight andproperties ideally suited for an inner ply of a multi-ply liner bag.Film B is preferably made from a film-forming resin that has anintrinsic viscosity of at east abo t 0.6 and a density not to exceed9.935, and properties suited for an outer ply of a multi-ply liner bag.

While it is preferred to form the inner and outer plies of the multi-plybags with polyethylene film herein described, other polyolefin filmsincluding polyethylene copolymers, polypropylene, copolymers of ethyleneand propylene, and mixtures of polyethylene and polypropylene, as wellas mixtures of such polyolefins and other film-forming polymers whichhave the aforedescribed properties, can be used. Desirably, the innerfilm ply of the multi-ply liner bag is made of film-forming polyolefinresins having an intrinsic viscosity of at least about 1.0 and the outerfilm ply is made of film-forming polyolefin resins having an intrinsicviscosity of at least about 0.6. Flexible thermoplastic films ha dug aflex modulus of at least about 25,000 pounds per square inch in thelongitudinal and transverse directions can also be used for the innerply of the multi-ply liner bags. Furthermore, flexible thermoplasticmaterials having a coefi'lcien: of friction of less than about 0.40 canbe used for the outer ply.

The size of the liner bag can vary, depending on the amount of fiowablematerial to be handle lne liner bag 10 or ill herein described andillustrated in the drawings has a five-gallon capacity. Liner bagshaving a three-gallon, ten-gallon capacity, etc. can also be used.

The number of plies for any given liner bag will depend on among otherthings, th weight, vol me and type of material to be contained in thebag, and the shipping conditions likely to be encountered. For example,the five-gallon, two-ply polyethylene liner bag 10 or ill hereindescribed and illustr ed is ideally suited for use in combination withthe rigid container 12 for shipping milk over rough country roads andstoring it for long periods of time. Where more than two plies aredesired, the intermediate plyfics) can be madeof fihn which is resistantto environmental stress corrosion and flex fatigue.

Depending upon the number of plies used, individual ply thickness needonly be /2, /3 or A as thick as a single ply liner. Moreover, multi-plyliner bags have been found to be stronger and more flexible than singlebags of the same total Weight or" material.

Each ply of film of the liner bag It? is self-supportin Films having athickness to provide the required durability, typically of .0610 to0.0030 inch or more, have been found satisfactory for such usage.

With respect to forming the essentially sterile multiply thermoplasticliner bag, the interior of melt-extruded flexible, thermoplasticseamless tubular film, such as that formed by the blown-tube methoddescribed in US. Fat en't 2,461,975, is sterile.

Accordingly, one method of fabricating the liner bags 10 of FIGS. 1-3 isby forming the inner film ply 14 from a continuous length of suchmelt-extruded flattened seam ess tubular film, and forming the outerconcentric film ply 16 by center-folding and circumscribing sheetingabout said continuous length of flattened seamless tubular film with thesheeting center-fold 13 in juxtaposition with one side of said flattenedseamless tubular film, and heat sealing the free edges 2% of thesheeting 16 together in juxtaposition with the other side of theflattened seamess tubular film. The bottom end 22 of the multi-ply linerbag 1t is formed by transversely heat sealing the inner and outer plies14, 16 of flattened seamless tubular film and center-folded heat sealed,tubular sheeting, toget er across the width of said bag 16). The top end2-5 of multi-ply liner bag 11 is formed by transversely heat sealingsaid inner and outer plies 14, 16 together, spaced from the heat seal ofthe bottom end 22, in such manner so as to leave a gap 32 in the corner38 adjacent the sheeting center-folded 1S. Thereafter, the thusly heatsealed film plies 14, 16 can be cut into unit bags 1t"; and the fillingand dispensing spout can be inserted in the gap 32 and open to theinterior of the inner film ply 14, to maintain the essentially sterileinterior of the inner film ply such as by inserting the rubber tube 34in'the gap 32, gathering the film plies 14, 16 into overlapped spiralledleak-proof folds about the tube 34, and fastening the twisted fold offilm plies 14, 16 such as by a conventional twist wire 43.

A production operation for the fabrication of liner bags for milkshipping containers made according to the described method is regularlytested for sterility of the liner bag interior. This test is conductedby the procedure described in the Standard Methods for the Ex aminationof Dairy Products, 11th Edition, 1960, published by the American PublicHealth Association, Inc. The allowable total bacterial colony count isstated in the regulation to be 18,906 for a five-gallon size of milkcontainer.

Assembled liner bags made by the described method are regularly testedon a production basis of. one test bag per 500 per operator. Ninety-fivepercent of bags tested are sterile. Five percent of the liner bags areshowing a total count of never more than 2 colonies per plate, or atotal of 100. Thus, it is seen that this method is a distin t and usefuladvance in the art of making shipping containers for milk.

in forming an interiorly essentially sterile multi-ply liner bag 1t) ofFIGS. -7, a continuous length of interiorly essentially sterileflattened seamless tubular film is also used as the inner ply 14' whilethe outer concentric ply 16 is formed by superimposing two she is 1'7,19 about the continuous length of flattened seamless tubular film, heatsealing the longitudinal edges 25.? of the sheets 17, 19 together injuxtaposition with the adjacent edges of the flattened seamless tubularfilm. Thereafter, the inner and outer plies 14, 16 can be transverselyheat sealed film plies 14', 16', cut into unit bags 16 with the tube 34'inserted into and fastened to tie multi-ply bag as hereinbeioredescribed for the rnultl-ply bag 1% of FIGS. 13.

The heat seals in the multi-ply inner bags herein described can beformed by well-known techniques, such as by a rotating heated sealingwheel cooperating with a resilient surface for the longitudinal heatseals and by an intermittently operated heated bar or impulse sealingbar for the transverse heat seals.

In using the multi-ply liner bags 10 for milk, a liner bag 10 is placedin a rigid container, such as the paperboard container 12 shown in FIG.7. The multi-ply bag 1% is that shown in FIGS. 1-3 but it is to beunderstood that the liner bag 16 of FIGS. 5-7 can be used instead. Theplug (not shown) in the tube or spout 34 is removed and after drawing avacuum on the liner bag 16, it is filled with a measured amount of milkin place in the container 12. The spout 34 is then closed otf again suchas by another plug and pulled through a hole 42 in one of the firstfolded flaps 44 of the container 12. The freeid board portion 41 of theliner bag 19 is thereafter loosely folded about the normal milk level.The spout 34 is then laid fiat upon the first fold flaps 44 and held inplace by the second fold flaps 46 of the container 10 when they arepasted down over the first fold flaps 44.

The milk containing container 12 is delivered to dairy customers, suchas restaurants and institutions. The tube or spout 34 is then Withdrawnby removing tabs 48 from the second fold flaps 46, the container 12 isinverted and placed into a refrigerated dispenser unit, and the tube 34threaded through a pinch valve (not shown). The plug in the tube 34 isremoved and the dispensing of the milk from the container 12 iscommenced.

In place of the milk, the multi-ply liner bag of the present inventioncan also be used for shipping, storing and dispensing other flowablematerials, including fruit juices, syrups, and other liquids, as well asice cream and pastry and pulverulent materials, such as pudding,jellies, cake mixes, etc.

It will be obvious to those skilled in the art that various changes andmodifications may be made in the foregoing description without departingfrom the spirit and nature of the present invention.

What is claimed is:

1. A flexible, leakproof, collapsible, multiply liner bag for perishablematerial such as milk and the like, comprising an inner ply of flattenedseamless tubular polyolefin film interiorly essentially sterile, and aconcentric coextensive outer ply of center-folded polyolefin sheetingcircumscribed about said inner ply, said center-fold of the sheetingbeing juxtaposed along one flattened edge of said seamless tubular innerfilm ply with the free edges of the sheeting opposite said center-foldheat sealed in juxtaposition with the other flattened edge of said innerseamless tubular film ply, one end of the coextensive inner and outerplies transversely heat sealed together across the width of themulti-ply liner bag and the other end of the coextensive inner and outerfilm plies transversely heat sealed together so as to leave a gap in onecorner of said multi-ply liner bag other end, and a spout open to theinterior of said seamless tubular inner film ply and in said gap,thereby providing a leakproot heat sealed multi-ply liner bag, the innerpolyolefin film ply being characterized by being resistant toenvironmental stress corrosion and flex fatigue, and the outerpolyolefin film ply being characterized by being resistant to punctureand abrasion.

2. A flexible, leakproof, collapsible, multi-ply liner bag forperishable material such as milk and the like, comprising an inner plyof flattened seamless tubular polyethylene film interiorly essentiallysterile, and a concentric coextensive outer ply of center-foldedpolyethylene sheeting circumscribed about said inner ply, saidcenterfold of the sheeting being juxtaposed along one flattened edge ofsaid seamless tubular inner film ply with the free edges of the sheetingopposite said center-fold heat sealed in juxtaposition with the otherflattened edge of said inner seamless tubular film ply, one end of thecoextensive inner and outer plies transversely heat sealed togetheracross the Width of the multi-ply liner bag and the other end or" thecoextensive inner and outer film plies transversely heat sealed togetherso as to leave a gap in one corner of said multi-ply liner bag otherend, and a spout open to the interior of said seamless tubular innerfilm ply and in said gap, thereby providing a leakproof heat sealedmulti-ply liner bag, the inner polyethylene film ply comprises afilmforming polyethylene resin having an intrinsic viscosity of at leastabout 1.0 and a density of not greater than 0.935 and is beingcharacterized by being resistant to environmental stress corrosion andflex fatigue, and the outer polyethylene film ply comprises afilm-forming polyethylene resin having an intrinsic viscosity of atleast about 0.6 and a density of not more than 0.935 being characterizedby being resistant to puncture and abrasion.

3. In combination with a rigid container, a flexible, leakproof,collapsible liner bag within said container for holding, shipping anddispensing a llov/able material having an inner ply of flattened seamess tubular polyolefin film interiorly essentially s eriie and aconcentric, coextensive outer ply of center-folded polyolefin sheetingcircumsc ibed about said inner ply, said center-fold of the sheetingbeing juxtaposed along one flattened edge of said inner seamless tubmarfilm ply With the free edges of the sheeting opposite said center-foldheat sealed in juxtaposition with the other flattened edge of said innerseamless tubular film ply, one end of the coextensive inner and outerplies transversely heat sealed together across the width of themulti-ply liner bag and the other end of the coextensive inner and outerplies transversely heat sealed together so as to leave a gap in onecorner of said multi-ply liner bag other end, and a spout open to theinterior of said sea .rless tubular inner film ply and in said gap,thereby providing a leakproof heat sealed muiti-ply liner bag, saidrnulti-ply liner bag being of such length so as to provide a freeooardportion to insure filling the flowable material to a precisepredetermined volume, thereby effecting a normal material level withinsaid multi-ply liner bag below the upper end thereof and with saidfreeboard portion being loosely infolded to said normal material level,the inner ply of said multi-ply liner bag comprising a polyolefin filmcharacterized by being resistant to environmental stress corrosion andflex fatigue primarily due to shipping motion Which causes the flowablematerial to "move in and about the film folds of the infolded freeboardportion, thereby flexing and unfiexing the folds therein, and the outerply of said multiply liner bag comprising a polyolefin filmcharacterized by being resistant to puncture and abrasion caused byhandling and contact with the rigid container.

4. in combination with a rigid container, at flexible, leakproof,collapsible liner bag Within said container for holding, shipping anddispensing milk having an inner ply of flattened seamless tubularpolyethylene film interiorly essentially sterile and a concentric,coextensive outer ply of center-folded polyethylene sheetingcircumscribed about said inner ply, said center-fold of the sheetingbeing juxtaposed along one flattened edge of said inner seamless tubularfilm ply with the free edges of the sheeting opposite said center-foldheat sealed in juxtaposition with the other flattened edge of said innerseamless tubular film ply, one end of the coextensive inner and outerplies transversely heat sealed together across the Width of themulti-ply liner bag and the other end of the coextensive inner and outerplies transversely heat sealed together so as to leave a gap in onecorner of said multi-ply liner bag other end, and a spout open to theinterior of said seamless tubular inner film ply and in said gap,thereby providing a lealcproof heat sealed multi-ply liner bag, saidlti-ply liner bag being of such length so as to provide a freeboardportion to insure filling the fiowable material t being loosely info dedto said normal material level, the inner polyethylene film ply of saidmulti-ply liner bag comprising a film-forming polyethylene resin havingan intrinsic of at least about 1.0 and a density of not greater than0.935 and characterized by being resistant to environmental stresscorrosion and flex fatigue primarily due to shipping motion which causesthe fiowable material to move in and about the film folds of theintolded freeboard portion, thereby flexing and unflexing the foldstherein, and the outer polyethylene film ply of said multiply liner bagcomprising a film-forming polyethylene resin having an intrinsicviscosity of at least about 0.6 and a density of not more than 0.935characte ized by being resistant to puncture and abrasion caused byhandling and contact with the rigid container.

5. in a continuous method of forming a mnlti-ply liner bag of fiexiole,lealcproof, collapsible film comprising forming an inner film ply from acontinuous length of melt-extruded flattened seamless flexiblethermoplastic tubular film interiorly essentially sterile, forming anouter concentric film ply by center-folding and circumscribing flexiblethermoplastic sheeting about said seamless tubular film with saidcenter-fold of the sheeting juxtaposed along one flattened edge of saidseamless tubular film, heat scaling the free edges of the sheetingopposite said centerfold together in juxtaposition with the otherflattened edge of aid seamless tubular film, transversely heat sealingthe concentric inner and outer film plies of flattened seamless tubularfilm and center-folded heat sealed sheeting together across the Widthsthereof, and transversely heat sealing said concentric inner and outerplies together spawd from the other transverse heat seal in such mannerso as to leave a gap in one corner of said inner and outer film plies,transversely severing said concentric plies of heat sealed seamlesstubular film and sheeting into unit multiply liner bags, and aflixing aspout to said multi-ply liner bag so as to be open to the interior ofthe inner ply of seamless tubular film and in said gap and rnm'ntain theessentially sterile interior of the seamless tubular film,

to form a leakproof multily liner bag interiorly $88611.

tubular film with said center-fold of the sheeting juxtaposed along oneflattened edge of said seamless tubular film, heat sealing the freeedges of the sheeting opposite said center-fold together injuxtaposition with the other flattened edge of said seamless tubularfilm, transversely heat sealing the concentric inner and outer filmplies of flattened seamless tubular film and center-folded heat sealedsheeting together across the width thereof, and transversely heatsealing said concentric inner and outer plies together spaced from theother transverse heat seal in such manner so as to leave a gap in onecorner of said inner and outer film plies, transversely severing saidconcentric plies of heat sealed seamless tubular film and sheeting intounit multi-ply liner bags, and aflixing a spout to said multi-ply linerbag so as to be open to the interior of the inner ply of seamlesstubular film and in said gap and maintain the essentially sterileinterior of the seamless tubular film, to form a leakproof multi-plyliner bag interiorly essentially sterile.

7. A flexible, lealcproof, collapsible, multi-ply liner bag forperishable material such as milk and the like, and having an inner plyof flattened seamless polyethylene film resistant to environmentalstress corrosion, flex fatigue and interioriy essentially sterile, andcomprising a filmforming polyethylene resin having an intrinsic of atleast about 1.0 and a density of not more than 0.935; and a concentric,coextensive ply of two sheets of polyethylene film resistant to abrasionand puncture and comprising a polyethylene resin having an intrinsic ofat least about 0.6 and a density of not greater than 0.935, said twopolyethylene sheets superimposed about the inner film ply with the freeedges of said two sheets heat sealed together in juxtaposition with theadjacent edges of said inner flat-- 13 ply and in said gap, therebyproviding a leakproof heat sealed multi-ply liner bag.

8. In combination With a ri id container, a flexible leakproof,collapsible liner bag within said container for holding, shipping anddispensing milk having an inner ply of flattened seamless tubularpolyethylene film and a concentric, coextensive outer ply of twopolyethylene sheets superimposed about said inner ply with thelongitudinal free edges of said two sheets heat sealed together injuxtaposition to the adjacent edges of the inner flattened seamlesstubular film ply, one end of the coextensive inner and outer pliestransversely heat sealed together across the width of the multi-plyliner bag, and the other end of the coextensive inner and outer pliestransversely heat sealed together so as to leave a gap in one corner ofsaid multi-ply liner bag other end, and a spout open to the interior ofsaid seamless tubular inner film ply and in said gap, thereby providinga leakproof heat sealed multiply liner bag, said multi-ply liner bagbeing of such length so as to provide a freeboard portion to insurefilling the flowable material to a precise predetermined volume, therebyeffecting a normal material level within said multiply liner bag belowthe upper end thereof and with said freeboard portion being looselyinfolded to said normal material level, the inner polyethylene film plyof said multi-ply liner bag comprising a film-forming polyethylene resinhaving an intrinsic viscosity of at least about 1.0 and a density of notgreater than 0.935 and characterized by being interiorly essentiallystreile and resistant to environmental stress corrosion and flex fatigueprimarily due to shipping motion which causes the flowable material tomove in and about the film folds of the ill-folded freeboard portion,thereby flexing and unflexing the folds therein, and the outerpolyethylene film ply of said multiply liner bag comprising afilm-forming polyethylene resin having an intrinsic viscosity of atleast about 0.6 and a density not greater than 0.935 and characterizedby being resistant to puncture and abrasion caused by handling andcontact with the rigid container.

9. In a continuous method of forming a multi-ply liner bag of flexible,leakproof, collapsible film comprising forming an inner film ply from acontinuous length of melt-extruded flattened, seamless flexiblethermoplastic tubular film interiorly essentially sterile, forming anouter concentric film ply by superimposing two sheets of flexiblethermoplastic film about said seamless tubular film, heat sealing thelongitudinal free edges of the two sheets together in juxtaposition withthe adjacent edge of the inner flattened seamless tubular film ply,transversely heat sealing the concentric inner and outer film plies offlattened seamless tubular film and longitudinal heat sealed sheetstogether across the widths thereof, and transversely heat sealing saidconcentric inner and outer plies together spaced from the othertransverse heat seal in such manner so as to leave a gap in one cornerof said inner and outer film plies, transversely severing saidconcentric plies of heat sealed seamless tubular film and sheeting intounit multi-ply liner bags, and afiixing a spout to said multi-ply linerbag so as to be open to the interior of the inner ply of seamlesstubular film and in said gap and maintain the essentially interior ofthe seamless tubular film, to form a leakproof mnlti-ply liner baginteriorly essentially sterile.

10. The method according to claim 9 wherein the multi-ply liner bag isused for milk; and wherein the inner ply of flattened seamless flexiblethermoplastic tubular film interiorly essentially sterile comprises afilm-forming polyethylene resin having an intrinsic viscosity of atleast 1.0 and a density of not greater than 0.935 and is resistant toenvironmental stress corrosion and flex fatigue, and the outer ply oftwo flexible thermoplastic sheets comprises a film-forming polyethyleneresin having an intrinsic viscosity of at least about 0.6 and a densityof not greater than 0.935.

References Cited in the file of this patent UNITED STATES PATENTS2,554,157 Snyder May 22, 1951 2,898,027 Scholle Aug. 4, 1959 2,973,119Parker Feb. 28, 1961 FOREIGN PATENTS 66,747 Denmark May 3, 1948 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,122,297February 25, we l John P., Sachs It is hereby certified that errorappears in the above numbered patent requiring correction and that thesaid Letters Patent should read as corrected below.

Column 2 line l5 for "containe" read container column 6; line 7, for".935" read 0935 column 7, line 32, for June 1054" read June 1954 line38 for "deliciters read deciliters column 8 line 66 for "@0010" read0.0010 column 12 lines 60 and 64, for "intrinsic of", each occurrence,read intrinsic viscosity of column 14, line 19, for "essentiallyinterior" read essentially sterile interior Signed and sealed this 14thday of July 19640 (SEAL) Attest:

ESTON G. JOHNSON EDWARD J. BRENNER Attesting officer Commissioner ofPatents

1. A FLEXIBLE, LEAKPROOF, COLLAPSIBLE, MULTI-PLY LINER BAG FORPERISHABLE MATERIAL SUCH AS MILK AND THE LIKE, COMPRISING AN INNER PLYOF FLATTENED SEAMLESS TUBULAR POLYOLEFIN FILM INTERIORLY ESSENTIALLYSTERILE, AND A CONCENTRIC COEXTENSIVE OUTER PLY OF CENTER-FOLDEDPOLYOLEFIN SHEETING CIRCUMSCRIBED ABOUT SAID INNER PLY, SAID CENTER-FOLDOF THE SHEETING BEING JUXTAPOSED ALONG ONE FLATTENED EDGE OF SAIDSEAMLESS TUBULAR INNER FILM PLY WITH THE FREE EDGES OF THE SHEETINGOPPOSITE SAID CENTER-FOLD HEAT SEALED IN JUXTAPOSITION WITH THE OTHERFLATTENED EDGE OF SAID INNER SEAMLESS TUBULAR FILM PLY, ONE END OF THECOEXTENSIVE INNER AND OUTER PLIES TRANSVERSELY HEAT SEALED TOGETHERACROSS THE WIDTH OF THE MULTI-PLLY LINER BAG AND THE OTHER END OF THECOEXTENSIVE INNER AND OUTER FILM FLIES TRANSVERSELY HEAT SEALED TOGETHERSO AS TO LEAVE A GAP IN ONE CORNER OF SAID MULTI-PLY LINER BAG OTHEREND, AND A SPOUT OPEN TO THE INTERIOR OF SAID SEAMLESS TUBULAR INNERFILM PLY AND IN SAID GAP, THEREBY PROVIDING A LEAKPROOF HEAT SEALEDMULTI-PLY LINER BAG, THE INNER POLYOLEFIN FILM PLY BEING CHARACTERIZEDBY BEING RESISTANT TO ENVIRONMENTAL STRESS CORROSION AND FLEX FATIGUE,AND THE OUTER POLYOLEFIN FILM PLY BEING CHARACTERIZED BY BEING RESISTANTTO PUNCTURE AND ABRASION.